X-ray image sensor and method for fabricating the same

Abstract

An X-ray image sensor having a photoelectric conversion part that converts X-ray photons into electric charges. The X-ray image sensor includes a pixel electrode for collecting the electric charges and a storage capacitor for storing the electric charges collected by the pixel electrode. The storage capacitor includes a first capacitor electrode, the pixel electrode, and a dielectric layer that is deposited on the first capacitor electrode. The pixel electrode contacts an electron transport electrode via a hole through the dielectric layer. A switching TFT controls the release of electric charges in the storage capacitor to an external circuit. The switching TFT is comprised of a gate electrode, a first insulation film, a drain electrode, and a source electrode that contacts the electron transport electrode.

What is claimed is:  
     
       1. An X-ray image sensor, comprising: 
       a substrate;  
       a gate electrode on the substrate;  
       a first insulation film on the substrate that covers the gate electrode;  
       an amorphous silicon film formed on the first insulation film over the gate electrode;  
       a doped amorphous silicon film defining a channel region for the amorphous silicon film on the amorphous silicon film;  
       source and drain electrodes on the doped amorphous silicon film that are spaced apart from each other;  
       a ground line on the first insulation film and that is spaced apart from the source and gate electrodes;  
       a second insulation film covering the ground line, the source and drain electrodes, amorphous silicon film, the channel region, and the first insulation film, the second insulation film including a first contact hole that exposes a portion of the ground line and a second contact hole that exposes a portion of the source electrode;  
       a first capacitor electrode on the second insulation film, the first capacitor electrode having an electrical connection with the ground line through the first contact hole;  
       an electron transport electrode on the second insulation film, the electron transport electrode having an electrical connection with the source electrode through the second contact hole;  
       a dielectric layer covering the second insulation film, the first capacitor electrode, and the electron transport electrode, the dielectric layer having a third contact hole that exposes a portion of the electron transport electrode; and  
       a second capacitor electrode on the dielectric layer, the second capacitor electrode having an electrical connection with the electron transport electrode through the third contact hole.  
     
     
       2. An X-ray image sensor according to  claim 1 , wherein the second capacitor electrode extends over the semiconductor film. 
     
     
       3. An X-ray image sensor according to  claim 1 , wherein the first and second insulation layers are made of a material selected from the group comprised of BCB (benzocyclobutene), acryl, and polyamide. 
     
     
       4. An X-ray image sensor according to  claim 1 , further comprising, an X-ray-sensitive material on the second capacitor electrode. 
     
     
       5. An X-ray image sensor according to  claim 4 , further comprising an X-ray transparent material on the X-ray-sensitive material. 
     
     
       6. An X-ray image sensor according to  claim 4 , wherein said X-ray transparent material includes a material from a group consisting of amorphous selenium, HgI 2 , PbO 2 , CdTe, CdSe, Thallium Bromide, and Cadmium Sulfide. 
     
     
       7. An X-ray image sensor according to  claim 1 , wherein said electron transport electrode is comprised of indium tin oxide. 
     
     
       8. An X-ray image sensor according to  claim 1 , wherein said second insulation film includes a material from a group consisting of benzocyclobutene, acryl, and polyamide.